In testing a work in progress of mine recently, I noticed that the game plays quite differently in V5 than it does in V4 (which it was written in). It throws up error messages quite frequently which I'm not entirely sure how to fix, and default messages I had overridden in the ALR are back to their original state. Anyone playing the game with the V5 Runner is going to run into all manner of problems with it, and I'm guessing the same will apply to anyone trying to play it via the WebRunner*.
Might it be an idea to warn anyone playing a V4 game with the V5 Runner that they're better off running it with the V4 Runner instead? And disable WebRunner play for V4 games by default? It's not doing ADRIFT any favours if the games are buggy because the player is using the wrong version of the software to run them.
* Which, incidentally, is throwing up the following error message when I try to run the latest V5 game on the main site: "The file is a later version than the software. It is advisable that you upgrade to ensure it runs properly." That's a pretty offputting error message.